A dye imaging in a silver halide-containing photographic material is formed by reacting an exposed silver halide with a color developer, generally a p-phenylenediamine compound. An oxidized form of the developer is produced which then reacts with a compound called a coupler to yield a dye. Full color reproduction of an image is generally achieved through a subtractive color process, in which the primary colors red, green and blue are reproduced by forming dyes of their complementary colors--i.e. cyan, magenta, and yellow, respectively. The subtractive color process is described in T. H. James, ed., The Theory of the Photographic Process, Fourth Edition, Macmillan, New York, 1977, pp. 336 ff.
For the formation of cyan dye images, the most commonly used couplers are variously substituted phenols and naphthols. A substituent of the coupler, called a coupling off group, is located at the position of reaction between the oxidized developer and the phenol or naphthol and is eliminated in the process of dye formation. In most color photographic materials, the coupler is incorporated in a layer containing silver halide and is immobilized in that layer by a high molecular weight ballast substituent on the coupler. Cyan couplers are discussed in The Theory of the Photographic Process, pp. 358 ff.
Various hydroxyquinoline compounds have been described as couplers in color photographic materials. U.S. Pat. Nos. 2,449,966, 2,455,169, and 2,584,349 disclose 8-hydroxyquinolines with arylazo coupling off groups, which can be used as masking couplers for color correction. U.S. Pat. No. 2,524,725 and 2,524,741 relate to 8-hydroxyquinoline couplers that react with o-phenylenediamine developers to form intermediate compounds that can be cyclized to form magenta-colored phenazonium dyes. The couplers disclosed in U.S. Pat. No. 2,886,436 are derivatives of 6-amino-8-hydroxyquinoline that undergo cyclization after reaction with oxidized p-phenylenediamine developer to product magenta-colored azine dyes.
U.S. Pat. No. 4,296,199 and 4,296,200 disclose a larger number of different types of cyan couplers with thiosubstituted alkoxy coupling off groups. Included amongst these compounds are hydroxyquinoline cyan couplers, but no specific structures are mentioned.
U.S. Pat. No. 4,770,988 discloses a broad class of cyan couplers used in combination with phenol cyan couplers, while U.S. Pat. No. 4,898,812 relates to the use of a cyan coupler in combination with a development accelerator contained in the same layer. Both U.S. Pat. Nos. 4,770,988 and 4,898,812 disclose one specific 8-hydroxyquinoline, containing a high molecular weight substituted benzamido group in the 7-position and a chloro coupling off group in the 5-position. There is no indication that this compound can be substituted at the 1 or 2 positions with alkyl ballast groups.
One of the most general synthesis of quinoline compounds is the Doebner-von Miller reaction, in which an aromatic amine is condensed with an .alpha.,.beta.-unsaturated carbonyl compound at high temperature in the presence of a strong acid (G. Jones, ed. "Quinolines," Part I, in A. Weissberger and E. C. Taylor, eds., The Chemistry of Heterocyclic Compounds, vol. 32, John Wiley & Sons, New York 1977, p. 100) as shown in the following formula: ##STR2## When R.sub.1 is --OH, the product is a hydroxyquinoline. Because of the drastic reaction conditions utilized in this process, the yield of desired product is low, and its separation from a mixture of tarry by-products is difficult. Many attempts have been made to improve the yield of quinoline compounds from this synthesis. For example, R. Manske et al., Can. J. Res. 27, 1949, p. 359 discloses a Skraup variation of the Doebner-von Miller reaction where a mixture of aminophenols, corresponding nitro compounds, and excess glycerol in concentrated sulfuric acid react and achieve good yields of hydroxyquinoline compounds as follows: ##STR3## wherein R is H or Cl Isolation and purification of the products of this reaction, were still tedious, and the use of glycerol precluded introduction of substituents into the heterocyclic nucleus.
Another approach to improving the synthesis of hydroxyquinoline utilized derivatives of the starting .alpha.,.beta.-unsaturated carbonyl compounds. For example, in Y. Oi, E. Omori, Jap. Pat. 70 16948, C.A. 73, 98820 (1970), 2-aminophenols were condensed with the diacetyl derivative of acrolein to yield 8-hydroxyquinolines as follows: ##STR4## Similarly, in H. J. Teuber, S. Benz, Chem. Ber. 100, 2918 (1967), 3-aminophenols reacted with 3-ethoxyacrolein diethyl acetal to give 5-hydroxyquinoline compounds as follows: ##STR5## However, as with the previous procedures, these latter two reactions did not allow for the presence of substituents in the heterocyclic ring.
The Doebner-von Miller synthesis and its variants are thus limited to the production of simple quinolines of low molecular weight. Further, the difficulty of preparing complex .alpha.,.beta.-unsaturated carbonyl compounds restricts the introduction of substituents into the heterocyclic nucleus. Finally, the drastic reaction conditions, i.e. strong acid and high temperatures, generally result in low yields of the desired products and difficult isolation of them from a myriad by-products. A need thus exists for a simple synthetic method, carried out under mild conditions, to produce hydroxyquinoline compounds and, particularly, the 8-hydroxyquinoline and 5-hydroxyquinoline cyan couplers of the present invention.